num_str='0123456789'
print(num_str[2:6])
print(num_str[2:])
print(num_str[-2:])
# 上面为截取末尾两个字符串
print(num_str[::-1])
# copy就是拷贝，地址不一样
def use_copy():
    a=[1,2,3]
    b=a.copy()
    a[0]=5
    print(b)

use_copy()